MEMS-actuated wavelength drop filter based on microsphere whispering gallery modes

MEMS-enabled tuneable optical coupling between optical microsphere resonators and optical fibre waveguides is reported. We describe the design, fabrication and experimental characterization of a MEMS platform, based on electrothermal actuators, which controls the resonator-to-waveguide separation. We compare the simulated and experimental displacements of the actuators in an unloaded and loaded state, where the load is a 1 mm optical spherical resonator. We then demonstrate the proof of concept application of selective wavelength dropping using the MEMS platform by modulating the coupling between the spherical resonator and a tapered optical fibre waveguide

Provincial and Local Governments in China: Fiscal Institutions and Government Behavior

What are the incentives faced by local officials in China? Without democratic institutions, there is no mechanism for local residents to exercise “voice”. Given the hukou registration system, local residents have little opportunity to threaten “exit” if they are unhappy with local taxes and spending. This paper explores an alternative source of incentives, starting from the premise that local officials aim to maximize the jurisdiction’s fiscal residual (profits), equal to local tax revenue minus expenditures on public services. In a Tiebout setting with mobile households, this objective should lead to efficient provision. What happens, though, if firms and economic activity but not people are mobile? The paper examines the incentives faced by local Chinese officials in this context, and argues that the forecasted behavior helps to explain both the successes and the problems arising from local government activity in China.

Polarization Energy Gradients in Combined Quantum Mechanics, Effective Fragment Potential, and Polarizable Continuum Model Calculations

A method that combines quantum mechanics (QM), typically a solute, the effective fragment potential (EFP) discrete solvent model, and the polarizable continuum model is described. The EFP induced dipoles and polarizable continuum model (PCM) induced surface charges are determined in a self-consistent fashion. The gradients of these two energies with respect to molecular coordinate changes are derived and implemented. In general, the gradients can be formulated as simple electrostatic forces and torques among the QM nuclei, electrons, EFP static multipoles, induced dipoles, and PCM induced charges. Molecular geometry optimizations can be performed efficiently with these gradients. The formulas derived for EFP∕PCM can be generally applied to other combined molecular mechanics and continuum methods that employ induced dipoles and charges

Charge Transfer Interaction in the Effective Fragment Potential Method

An approximate formula is derived and implemented in the general effective fragment potential (EFP2) method to model the intermolecular charge transferinteraction. This formula is based on second order intermolecular perturbation theory and utilizes canonical molecular orbitals and Fock matrices obtained with preparative self-consistent field calculations. It predicts charge transferenergies that are in reasonable agreement with the reduced variational space energy decomposition analysis. The formulas for the charge transfer gradients with respect to EFP translational and rotational displacements are also derived and implemented

Modeling styrene-styrene interactions

This study is the first step in the systematic investigation of substituted (carboxyl) polystyrene nanoparticles. Understanding the fundamental interactions between the p-carboxyl styrene monomers, where an ethyl group is used instead of a vinyl group (referenced, for convenience, as p-carboxyl styrene ), provides the basic information needed to construct potentials for nanoparticles composed of these monomers. In this work, low-energy isomers of p-carboxyl styrene dimer were studied. The dimer structures and their relative and binding energies were determined using both Møller-Plesset second-order perturbation theory (MP2) and the general effective fragment potential (EFP2) method. Sections of the intermolecular potential energy surface (PES) of the p-carboxylated styrene dimer in its global minimum orientation were also determined. As expected, double hydrogen bonding between the two carboxylic groups provides the strongest interaction in this system, followed by isomers with a single H-bond and strong benzene ring-benzene ring (π-π) type interactions. Generally, the EFP2 method reproduces the MP2 geometries and relative energies with good accuracy, so it appears to be an efficient alternative to the correlated ab initio methods, which are too computationally demanding to be routinely used in the study of the more-complex polymeric systems of interest

A cross-sectional study of maternal perception of fetal movements and antenatal advice in a general pregnant population, using a qualitative framework

BACKGROUND: Maternal perception of fetal movements has been used as a measure of fetal well-being. Yet a Cochrane review does not recommend formal fetal movement counting compared to discretional fetal movement counting. There is some evidence that suggests that the quality of fetal movements can precede quantitative changes however there has been almost no assessment of how women describe movements and whether these descriptions may be useful in a clinical setting. Therefore we aimed to examine maternal perception of fetal movements using a qualitative framework. METHODS: Using a cross-sectional design we identified women during routine antenatal care at a tertiary referral hospital, in Sydney, Australia. Eligible women were pregnant ≥ 28 weeks, carrying a single child, > 18 years old, and with sufficient English literacy to self-complete a questionnaire. Post-natally the medical records were reviewed and demographic, pregnancy and fetal outcome data were extracted. Text responses to questions regarding maternal descriptions of fetal movements throughout pregnancy, were analysed using thematic analysis in an explicit process. RESULTS: 156 women participated. There was a general pattern to fetal movement descriptions with increasing gestation, beginning with words such as “gentle”, to descriptions of “strong” and “limb” movements, and finally to “whole body” movements. Women perceived and described qualitative changes to fetal movements that changed throughout gestation. The majority (83%) reported that they were asked to assess fetal movements in an implicit qualitative method during their antenatal care. In contrast, only 16% regularly counted fetal movements and many described counting as confusing and reported that the advice they had received on counting differed. CONCLUSIONS: This is the first study to use qualitative analysis to identify that pregnant women perceive fetal movements and can describe them in a relatively homogenous way throughout pregnancy that follow a general pattern of fetal growth and development. These findings suggest that women’s perception of fetal wellbeing based on their own assessment of fetal movement is used in an ad hoc method in antenatal care by clinicians

Massive Quiescent Cores in Orion. -- II. Core Mass Function

We have surveyed submillimeter continuum emission from relatively quiescent regions in the Orion molecular cloud to determine how the core mass function in a high mass star forming region compares to the stellar initial mass function. Such studies are important for understanding the evolution of cores to stars, and for comparison to formation processes in high and low mass star forming regions. We used the SHARC II camera on the Caltech Submillimeter Observatory telescope to obtain 350 \micron data having angular resolution of about 9 arcsec, which corresponds to 0.02 pc at the distance of Orion. Our analysis combining dust continuum and spectral line data defines a sample of 51 Orion molecular cores with masses ranging from 0.1 \Ms to 46 \Ms and a mean mass of 9.8 \Ms, which is one order of magnitude higher than the value found in typical low mass star forming regions, such as Taurus. The majority of these cores cannot be supported by thermal pressure or turbulence, and are probably supercritical.They are thus likely precursors of protostars. The core mass function for the Orion quiescent cores can be fitted by a power law with an index equal to -0.85$\pm$0.21. This is significantly flatter than the Salpeter initial mass function and is also flatter than the core mass function found in low and intermediate star forming regions. Thus, it is likely that environmental processes play a role in shaping the stellar IMF later in the evolution of dense cores and the formation of stars in such regions.Comment: 30 pages, 10 figures, accepted by Ap

Direct Total Syntheses of Frenolicin B and Kalafungin via Highly Regioselective Diels-Alder Reactions

Frenolicin B, an anticoccidial agent, has been synthesized in six steps from ketone 3. Racemic kalafungin, an antifungal agent, has been synthesized in five steps. The key step in both syntheses, a regioselective Diels-Alder reaction, proceeds with complete regiocontrol and in excellent yield. One rationale for the remarkable stereocontrol is that the lactone ring induces ring-puckering in the quinone subunit which, in consort with electrostatic repulsion, contributes to the regioselectivity